The question of 17th-century tonality has intrigued scholars for years: how to make sense of a repertoire in which modal concepts appear to coexist with elements of common-practice tonality. Although the system of modes and that of modern tonality are different constructions, the aspect of functional tonality that allows for the presence of major and minor keys at all 12 levels of transposition developed in part from an extension of a technique carried over from modal practice, that of transposition of mode. Nowhere is this process of tonal expansion based on the concept of transposition of mode as clear or as well structured as in the music of Giacomo Carissimi (1605-1674), the Roman composer of oratorios, cantatas, and motets whose output spans the central 40 years of the 17th century. A close examination of Carissimi's music provides us with a snapshot of the expansion of tonality via transposition and, in addition, offers important suggestions for understanding the tonal practices of contemporaries such as Monteverdi and Cavalli. In Carissimi's music, four basic tonalities are still clearly distinguishable, recognizable through unique and predictable cadence patterns. They appear at transposition levels ranging from the three-flat to the three-sharp systems, with the one-flat system conspicuous in its absence. As shown, the core of eight central keys demonstrates key pairing in a way that models the traditional authentic-plagal relationship of modes. An overview of Carissimi's tonal system demonstrates how the ap- parent coexistence of functional tonality and much older concepts of mode and hexachord can be understood to be part of a rational and organized system. This study explores Carissimi's tonal scheme through an examination of his cantatas, the repertoire displaying the widest tonal range. Based on characteristic cadence frequencies, opening transpositions, and previously unrecognized standard cadence patterns, it is possible to determine the nature of the four primary tonalities and their relationships to one another. These cadence patterns also appear as organizing principles in works of several other 17th-century composers and suggest future avenues of research. The final section summarizes the conservative and progressive features of Carissimi's tonal system, relates his practice to discussion of transposition in two popular treatises of the time, Giovanni Maria Bononcini's Musica prattico and Lorenzo Penna's Li primi albori musicali, and compares Carissimi's practice to the system of church keys (based on common transpositions of the psalm tones) prevalent in the 17th century. A study of Carissimi's cantatas thus reveals the existence of a truly distinct 17th-century tonal practice which functions on its own terms at the same time as it exhibits concepts derived from traditional modal and hexachordal theory, as well as contemporary practices of psalmody and small-scale functional tonality.
